Shielded switch assembly



Feb. l0, 1953 c. T. GRAUER 2,628,297

SHIELDED SWITCH ASSEMBLY Filed Sept. 20, 1946 IN VEN T01? ga/F @ogg/rauw lu/,4W

ATTORNEY Patented Feb. 10, 1953 UNITED STATES PATENT OFFICE SHIELDED SWITCH ASSEMBLY Carl T. Grauer, Oakland, Calif., assigner to the United States of America as represented by the United States Atomic Energy Commission Application September 20, 1946, Serial No. 698,371

(Cl. 20D-87) 2 Claims. l

This invention relates to flow switches and more particularly to a magnetically operated flow switch particularly adapted for use in the neighborhood of a strong disturbing magnetic field and in which means is incorporated for neutralizing the effect of this disturbing magnetic eld.

While the invention is of general application, it is particularly useful for regulation of the ow of liquids employed in connection with a calutron, which is an electromagnetic device for the separation of isotopes of polyistopoic material and which employs powerful electromagnets setting up magnetic fluxes which may reach the order of 4000 gauss.

It is accordingly an object of this invention to provide an improved magnetically controlled flow switch capable of neutralizing any disturbing magnetic fields in its environment.

It is a further object of this invention to provide a magnetically controlled flow switch which is magnetically shielded from any disturbing magnetic field to which the device may be exposed.

It is a feature of this invention to provide a magnetically controlled flow switch employing a ferromagnetic shield in the region of the magnetic control elements and coils adapted to set up either an alternating magnetic flux or a magnetic ux whose direction is opposed to the direction of the disturbing magnetic field.

Further objects and advantages will be apparent from the annexed specification in which:

Figure 1 is an elevation, partly in section, of a flow switch embodying the present invention; and

Fig. 2 is a section taken along the line 2-2 of Fig. 1.

Referring more particularly to the drawings, there is shown 9, ow switch or rotameter of more or less conventional design but incorporating the magnetic shielding features of this invention. The iiow switch includes a metering device indicated generally at 4 connected in a conduit 5, liquid iiowing through the conduit and the metering device along the path indicated by the arrows. The numeral 8 indicates a vertically disposed transparent tapering tube through which the liquid passes upwardly. A iloat 'I is disposed within the tube 6 and assumes a height corresponding to the rate of flow, which rate of flow may be read directly on the scale 3. The float 'I is secured to a rod la on the lower end of which is carried a soft iron plunger 8. A tubular member 9, of brass or other nonmagnetic material, surrounds the plunger 8 and communicates 2 with the interior of the metering device 4 so as to permit free movement of the plunger 8 in a vertical direction in accordance with the rate of flow.

A tubular member I0 of soft iron or other ferromagnetic material is secured to the base of the meter 4, as by set screw Ia, concentric with the tubular member 9. The bottom of the member I0 is closed by an end plate I2 of the same material. The members I0 and I2 serve as magnetic shields for the instruments enclosed therein.

A U-shaped permanent magnet II is arranged to be set at a predetermined height within the tubular member Il) corresponding to the rate of ilow at which the operation of the switch is desired. The permanent magnet has a pair of projecting segments I3 between the main opening I4 of the magnet and the gap I5 formed between the pole tips. A mercury switch I6 is disposed within the opening I4. The tube 9 is disposed between the pole tips of the magnet I I.

The mercury switch I6 comprises a lead II which is in permanent contact with a small pool I8 of mercury at the bottom end of the mercury switch. A second lead I9 includes a coil spring 30 biasing a small armature 20 to which is attached a bent wire I9a adapted to be moved into or out of contact with the mercury pool I8. The armature 20 is disposed adjacent the two projecting segments I3 of the magnet II.

When the conditions of iiow are such that the plunger 8 is disposed within the tube 9 exterior to the gap of the magnet II a relatively large portion of leakage ilux passes through the armature 28, drawing it toward the gap I5 against the action of the spring 30, thus causing the wire I9a to engage the mercury pool I8 and closing the mercury switch. The circuit including the mercury switch I8 may include an alarm to indicate that insu'icient fluid is being passed by the meter.

When the plunger 8 enters the gap of the magnet II, the amount of leakage flux passing through the armature 20 is reduced to a point where the hair spring 30 draws the armature 20 away from the gap I5, thus opening the mercury switch I6.

Mounted on each end of the tubular member I0 is a coil, indicated respectively at 26 and 21, connected in series and leading to suitable sources of potential 28. The coils 28 and 2l may be energized by either direct or alternating current, though direct current is preferred, as care must be taken in the case of alternating current to prevent the demagnetizing of the permanent magnet I I.

When the device above described was utilized in connection with metering uid to a calutron having a field of approximately li000 gauss, it was discovered that without energizing the coils 26 and 21, the magnetic field of the calutron disturbed the operation of the meter to 9, point where it became inoperative, while when a direct current producing 200 ampere turns was passed to the coils in such a direction as to oppose the field of the calutron, the meter became operative even though a wide fluctuation in the eld strength of the calutron was permitted. Furthermore, the meter remained operative when the coils were thus energized, even when the calutron field was turned oi, the iield of the coils 26 and 2i being insufficient alone to prevent operation of the meter but being sumcient to oppose the eld of the calutron to a point where the meter became operative. n

While there is described what is at present considered a preferred embodiment of the invention, it will be understood that various changes and modifications may be made therein without departing from the spirit of the invention and it is intended'to cover all such changes and modifications as come within the true scope and spirit of theappended claims.

What is claimed is:

Y 1. In combination with a rotameter for use in magnetic 'elds and having a vertical metering tube and a metering float adapted for free up and down movement within said tube, an elongated vmember connected to said. oat and extending vertically therefrom beyond said metering tube, a permanent magnet having a gap therein, a soft iron slug disposed at the free end of said elongated 'rnemben means for guiding said soft iron slug into and out of said magnet gan, an electrical switch having a magnetically actuated movable contact element disposed proximate to but inwardly of said gap, whereby downward Y and switch and having also a continuous wall extending across the lower end thereof, and a pair of serially connected coils disposed in spaced and surrounding relation about said shield for providing upon energization and with said shield eiective neutralization of external magnetic elds.

2. In combination with a rotameter for use in magnetic iields and having a Vertical metering tube and a metering oat adapted for free up and down movement within said tube, an elongated member connected to said float and extending vertically therefrom beyond said metering tube, a permanent magnet having a gap therein, 9, soft iron slug disposed at the free end of said elongated member, means for guiding said soft iron slug into and out of said magnet gap,

Van electrical switch having a magnetically actuated movable contact element disposed proximate to but inwardly of said gap, whereby upon downward movement of said oat said slug is moved into said gap changing the magnetic force aiecting Said element for actuating same, a cylindrical ferromagnetic shield surrounding said magnet,

Vslug and switch and having a longitudinal slot therein for adjustably mounting said magnet and a circumferential slot for accommodating orientation of said shield with respect to said rotameter, screw means extending through said circumferential slot into said rotameter for holding the latter in xedrelation to said shield, a pair of spacedV coils encircling said shield and disposed one at each end of the latter, andserial connections for energizing said coils to effect within said shield neutralization of external disturbing magnetic fields.

CARL T. GRAUER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 650,915 Scribner et al June 5, 1900 1.560,7'78 Goddard Nov. 10, 1925 1 '108,936 Cioni Apr. 16, 1929 2,187,369 Uehling Jan. 16, 1940 2,250,738 Wittmann July 29, 1941 2.419.942 Brewer May 6. 1947 

